Advanced Safety Vehicle (ASV) technologies have been developed in addition to technologies that have been used so far and are mainly intended for occupant protection after a collision. The ASV technologies arc mainly intended for prevention and avoidance of accidents by utilizing information/communication and electronic technologies. The ASV technologies focus on driver supports for safe driving, and these supports include recognition support, judgment support, operation support and the like, if the ASV technologies are put into practical use, it will become feasible to detect a forward obstacle using a radar technology or the like and to notify and alert a driver to the obstacle once the obstacle is detected.
A warning light for this type of highly emergent notification is preferably located at the center of a view (central view) of a driver when the driver casts his eyes to the front. Thus, the driver can recognize the notification even when the driver looks away from a meter panel at a seating position. However, the warning light provided at the center of the view may obstruct the driver's sight while driving.
A Head-Up Display (HUD) device (hereinafter, referred to as HUD) has been proposed as a technology which resolves such a technological problem and ensures both visibility and a view. The HUD enables displayed information to be visually recognized as a virtual image in the sight ahead of the driver. For the HUD of a motorcycle, a technology is used in which optical information irradiated from a luminous element such as LED is reflected off a windshield, and the reflected light enters eyeballs of the driver. This technology is disclosed in, for example, Japanese Patent Laid-Open Publication NO. 2001-278153.
In the above-mentioned known HUD, the light irradiated from a light source is required to enter into the eyeballs of the driver after being reflected off a windshield. However, the position, angle, size, material and the like of the windshield is limited by the aerodynamic characteristics, design, strength and the like of the motorcycle. Therefore, an optical path has to be adjusted only by mounting positions and direction angles of the luminous elements. However, in order to enter the light reflected off the windshield into the eyeballs of the driver, the luminous elements have to be placed at extremely limited positions between the meter panel and the windshield in a general motorcycle structure. Under such a limitation, there is a low degree of flexibility in the position and the direction angle of the luminous elements. Ultimately, the limitation may hamper an expanded application of the HUD to various vehicle models.
Furthermore, since positions of the driver's eyeballs vary in accordance with a frame, a seating posture, a seating position and the like of the driver, it is required to scatter the reflected light over a relatively wide area. However, when the windshield is used as a reflection medium, it is difficult to scatter the light over the wide area using the surface thereof, thus causing uneven levels of visibility depending on the driver.
An object of the present invention is to provide a vehicle display device which resolves the foregoing problems of the known technologies, provides excellent visibility and does not obstruct a sight ahead of a driver regardless of a frame and a seating position and the like of the driver, and a light guide plate thereof.